Guide pin and bushing assembly for flask, patterns, and the like

ABSTRACT

A two-part bushing or guide pin for aligning foundry flasks, hotboxes, and the like comprising: a machinable body portion having external threads for threading into a flask, hotbox, etc., and internal threads for receiving either a hardened nonmachinable guide ring or a hardened nonmachinable guide pin.

United States Patent Gerald R. Rusk Maumee, Ohio;

Robert E. Koch, Ottawa Lake, Mich. 857,819

Sept. 15, 1969 Oct. 12, 197 l The Freeman Supply Company Toledo, OhioInventors Appl. No. Filed Patented Assignee GUIDE PIN AND BUSHINGASSEMBLY FOR FLASK, PATTERNS, AND THE LIKE 3 Claims, 11 Drawing Figs.

vs. C: .4 164/385 1111.01 1312; 21/10 Field 61 Search 164/385-390,

[56] References Cited UNITED STATES PATENTS 2,451,747 10/1948 Kindt.14/387 UX 3,022,553 2/1962 Hines 1 164/387X 3,048,904 8/1962 Kloster164/390 3,379,239 4/1968 Rusk et al. 164/387 Primary Examiner J. SpencerOverholser Assistant Examiner-John S. Brown Attorney-William P. HickeyGUIDE PIN AND BUSHING ASSEMBLY FOR FLASK, PATTERNS, AND THE LIKE In thecase of the hardened nonmachinable guide ring, the outer surfaces areprovided with hardened ground threads adapted to be threaded into theinternal threads of the main body portion. Suitable means is providedfor locking the ring in angular relationship with the body after it isthreaded therein. The construction permits the main body portion of thebushing to be firmly seated and locked in a flask, etc., following whichthe hardened ring can be rotated within the main body portion until itssurfaces are accurately angularly positioned relative to the flask, andthe ring then locked to the bushing. The locking means may comprise anopening through the sidewalls of the ring for receiving a staking toolfor deforming the internal threads of the main body portion. A]-ternatively, a longitudinally extending hemicylindrical groove may beprovided in the periphery of the hardened ring, and the adjacent portionof the body drilled, to receive a soft metal locking pin.

In the case of the guide pin, it is provided with a ground and hardenedguide pin insert having external ground threads adapted to be insertedinto the softer machinable body portion. The guide pin insert mayinclude the hemicylindrical groove for locking it to the machinable bodyportion.

BACKGROUND OF THE INVENTION The foundry art has three general types ofprocesses for producing castings. In one type of process, thehalf-sections of a pattern are accurately secured to flat surfaces andusually to the opposite sides of a flat pattern plate. A foundry flaskthat is a rectangularly shaped box having open top and bottom sides isaccurately positioned against one side of the pattern plate, and afoundry sand containing a clay or other type of binder is tarnped aroundthe pattern section. The flask and pattern are inverted and the patternplate lifted from the top of the flask to expose the surface of the sandhaving a cavity therein conforming to the pattern section. Thereafterthe sand is dried and its binder hardened and the process is repeatedfor the other half-section of the pattern. The two flasks having themold cavities therein, are accurately booked or aligned, as will laterbe explained, to provide the total cavity into which molten metal ispoured.

In another type of process which makes what are called shell molds," thetwo half-pattern sections are made of metal and each is accuratelyinstalled upon the flat surface of a metal plate or plates. This plateis made to be a part of the pattem-heating box of a large machine calleda shell mold forming machine. Such a machine also includes arectangularly shaped sand tank which holds resin-coated sand and whichmust be accurately positioned on top of the pattem-heating boxcontaining the pattern and pattern plate. The pattemheating boxcontaining the pattern section is placed on top of the sand tank, andthe sand tank and heating box inverted so that binder-coated sand in thesand tank falls down on top of the heating box and pattern section. Thebox and pattern section are heated so that the resin-coated sandadjacent the heated surfaces of the pattern section and box becomehardened to a depth of approximately one-half inch to provide a shell"of sand and cured resin. The said tank and heating box are inverted toallow the loose sand to fall back down into the sand tank, and the"shell" containing an accurate impression of the pattern section isremoved from the pattern plate. This process is repeated with respect tothe pattern plate containing the other half-section of the pattern, andthe two shells" are thereafter cemented together to form the totalcavity that is to be filled with the molten metal. The booked andcemented shells are embedded in sand or metal shot to a sufficient depthto withstand the hydrostatic head of the molten metal.

The third type of process commonly used is called the hotbox process"which is similar to the shell-molding" process but differs principallytherefrom in that the box surrounding the pattern is heated, and theresin-coated sand is introduced into the heated box from a separatecontainer. In the hotbox process, the resin surrounding the pattern iscured in depth to form a finished cured mold.

In the processes above described, it is essential that the twohalf-sections of the pattern be accurately located'on pattern plates,and that these pattern plates be accurately located relative to theflasks, hotboxes, etc. in order that the molded sand will have side orother reference surfaces which can be easily aligned with respect toeach other.

In the first-described process, it is necessary to accurately registerthe pattern plate and flasks and thereafter accurately register theflasks containing the half-mold sections. In the second or thirdprocesses above described, it is necessary to accurately position orregister the pattern plate with the sand tank, or hotbox, used to formthe molds. In any of the processes given above, the means which has beenfound most convenient for performing the necessary alignment, comprisesthe use of a plurality of cooperating pins and bushings, the pins ofwhich are received in accurate internal guide surfaces of the bushings.In those instances where large castings are to be made, it is relativelyimpossible to obtain equal thermal expansion of all mated metal parts ofthe equipment when heated to cure the resin of the coated sand. Themeans customarily used to accommodate the difference in thermalexpansion is the utilization of at leastone bushing containing a roundopening which tightly engages the pin, while the bushings which arepositioned remotely therefrom, contain elongated openings havinginternal parallel guide surfaces that are oriented in the direction ofthermal expansion. The elongated bushings of the prior art have been oftwo general types: the first of which has external threads which extendthrough the flask, or the hotbox, as the case may be, and which aresecured in place by a nut on the back side of the member in which it isinstalled. Whenever one of these bushings becomes damaged, or the guidepin becomes broken, it is necessary to take the flask, the shell-moldingmachine, or the hotbox machine, as the case may be, out of operation anddrill or fish out" the broken pin or bushing.

The most commonly used type of bushing has been one with plaincylindrical side surfaces, which surfaces are provided with aninterference fit relative to the receiving openings which are made inthe flasks, pattern-heating boxes, hotboxes, etc. in which they are tobe installed. The bushings are installed with its internal oblongopening eyeballed" in the direction of thermal expansion. The bushing isthereafter, pressed into the receiving opening. Some rotation of thebushing usually always takes place while it is being pressed down intothe receiving opening, so that the installed bushing is not properlyaligned, and undue wear of the guide pins and bushings occurs.

A further difficulty with the prior art guide bushings and pins hasoccurred by reason of the continuing heating up and cooling down of theequipment in which the pins and bushings are installed. If this heatingup and cooling down is not accompanied by condensation, the bushing mayeventually loosen up in its receiving opening. In most instances,however, some condensation is present, and in this instance, thebushings and pins, and particularly the pressed-in bushings and pinsbecome frozen into the equipment into which they are installed,particularly where the equipment is cast aluminum. The removal of thebushings or pins is made difficult because they are hardened towithstand the abrasion of the foundry sand and are, substantially,nonmachinable. In many instances the equipment must be removed to amachine shop where the best available equipment and techniques areavailable for fishing the bushing out of the equipment.

Pins and bushings of the press fit type are usually made in an originalequipment size, plus at least two oversizes. Each oversize pin orbushing is used to replace the next smaller size pin or bushing. Notonly is the removal of the pins and bushings difficult and costly, butthe warehousing, selecting and installation of the replacement items isexpensive.

An object of the present invention, therefore, is the provision of a newand improved bushing the guide surfaces of which can be more accuratelypositioned in the equipment in which the bushing is installed than canthe prior art bushings.

A further object of the present invention is the provision of a new andimproved guide bushing which can be easily removed and new guidesurfaces installed without the removal of the equipment in which thebushing is installed to machine shops, etc.

Further objects and advantages will become apparent to those skilled inthe art from the drawings and following description of the preferredembodiments.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a cylindricalbushing assembly of the present invention;

FIG. 2 is a plan view of the bushing assembly shown in FIG.

FIG. 3 is a sectional view of the body portion of the bushing assemblyshown in FIGS. 1 and 2;

FIG. 4 is a plan view of the body section shown in FIG. 3;

FIG. 5 is a sectional view of the hardened ring shown in the assembly ofFIGS. 1 and 2;

FIG. 6 is a plan view of a hardened ring having a cylindrical internalguide surface;

FIG. 7 is a sectional view of the hardened ring shown in FIG.

FIG. 8 depicts a first stage of the preferred method of accuratelyinstalling the guide bushings of the present invention relative to theircooperating guide pins;

FIG. 9 depicts a second stage in the installation of the pins andbushings of the present invention;

FIG. 10 is a sectional view through a guide pin and bushing of thepresent invention, and depicts the final stage of the installation ofthe bushings and pins of the present invention; and

FIG. 1 I is a plan view of the guide pin shown in FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The guide pins and bushings ofthe present invention, whether they contain a pin, an internalcylindrical guide surface, or an oblong opening having parallel guidesurfaces, are formed in two pieces. The bushing comprises an outer bodyportion 10 having an external flange I2 at its upper end, and acylindrical centering surface 14 immediately beneath the flange. Thelower end of the body portion is provided with external threads 16 bymeans of which the body member can be threaded into and thereby securedto the flask, hotbox, or other member which is to be accuratelypositioned relative to another member. The body member 10 is providedwith suitable wrench-engaging surfaces, as for example a pair ofrectangular grooves 18 that are cut through opposite sides of the flangel2 and which are adapted to receive suitable designed tangs of a wrench.Body member 10 may further include transverse slots 20 that are milledor otherwise cut across the top surface of the flange 12 to a suitabledepth for receiving a flat blade of a wrench. In some instances, thebody 10 may be provided with both the grooves and the slots 20.

The body member 10 has a longitudinally extending opening 22therethrough, the upper end of which is suitably threaded as at 24. Thebody member 10 preferably also includes four longitudinally extendinggrooves 26, in the sidewalls of the opening 22 and which are shaped andpositioned to receive the corners of a square bar when slidlongitudinally into the opening 22. Where the ID. of the threads 24 isthe same as that of the sidewalls 22, the grooves 26 will extend throughportions of the threads 24. The grooves 26 are preferably broached orotherwise formed in the sidewalls of the opening 22 prior to the timethat the threads 24 are made. Grooves 26 may not be necessary in allinstances, but are to be preferred as providing additional means forapplying torque to the body 10 which has become frozen in an opening ofthe equipment in which it is installed. The sidewalls of the opening 22can be broached or otherwise conveniently made concentric with thecylindrical surface 14, and the structure so far described is made of amachinable material and is not hardened to a nonmachinable condition.

The bushing of the present invention also includes a hardened ring 28having external ground threads 30 which are otherwise accurately formedfor close engagement with the threads 24. The ring 28 has alongitudinally extending cylindrical opening 32 therethrough, andsuitable wrench-engaging surfaces for threading the ring 28 into and outof the upper end of the body member 10. In the preferred embodiment ofring 28 shown in the drawings, the sidewalls of the opening 32 areprovided with four longitudinally extending grooves 34 which are shapedand positioned to receive the comer edges of a square-shaped bar wheninserted into the opening 32. Alternatively wrench-engaging recesses 35through the ring may be provided or both the grooves 34 and recesses 35may be provided. The opening 32 and grooves 34 and recesses 35 arepreferably formed when the ring 28 is in a machinable condition andprior to hardening of the ring. The surface of the opening 32 maythereafter be ground slightly as may be necessary to insure its accuracyafter hardening, and this surface then used for centering during thegrinding operation. Where other types of wrench-engaging surfaces areused, as for example slots across the top face of the ring, thesesurfaces are preferably also formed before hardening. The ring 28includes a locking provision which may be the recesses 35, or in thepreferred embodiment, comprises one or more openings or recesses 36which extend through the sidewalls of the ring 28 between the sidewallsof the opening 32 and the threads 30 and through which a staking toolcan be inserted to deform the threads 24. As another means of lockingthe ring 28 into the bushing body 10, the external surface of the ring28 may be provided with a hemicylindrical groove 38 formed preferablybefore hardening. When the ring 28 is angularly positioned, and it isdesired to lock it into the body 10, the groove 38 can be used to centera drill for machining away portions of the body 10, including portionsof the thread 24 to complete a cylindrical opening for the reception ofa steel dowel pin or the like.

The ring structure so far described may be used for guide pins havingcylindrical guide openings 32. In those instances where the guide ringis to have an oblong opening 40 (see FIGS. 6 and 7) for accommodatingthermal expansion of the member whose guide pin it is to receive, asimilar structure will be used excepting that the internal opening 40 ofthe ring will be oblong as shown in FIG. 6. This oblong opening 40 canbe made by first drilling an opening, smaller than required, andthereafter broaching the opening into the oblong configuration 40. Ringscontaining the oblong opening 40 will, of course, have the externalthreads 30, a recess 35 or 36, or groove 38, or both. Bushings havingthe oblong opening 40 are also preferably machined before hardening. Theoblong opening 40 need not be exactly as shown in FIG. 6, so long as ithas parallel side portions 42 accurately ground or otherwise machined toengage opposite sides of a pin of predetermined diameter. These bushinginserts having an oblong opening may be threaded into the body portion10 by a wrench having an oblong surface generally corresponding to theoblong opening 40.

In the preferred method of installation and use of the bushings of thepresent invention, the flask, hotbox, or other member in which thebushing is to be installed is superimposed on a pattern plate and/orflask, hotbox or other member to which it is to be accurately aligned. Alongitudinal opening 44 is drilled through both members when accuratelyaligned as shown in FIG. 8. The opening 44 is either accurately drilledor otherwise machined to have a diameter either equal to or slightlyless than the root diameter of the threads I6 of the body portion 10.Thereafter the member in which the bushing is to be installed, isseparated from the booked member. and a counterbore 46 is made having adepth greater than the distance between the end of the cylindricalsection 14 and top of the flange 12. A larger counterbore 48 is thenformed to receive the flange l2, and the threads 50 are tapped into orotherwise formed in the opening 44 beneath the counterbore 46. It willbe seen that a body member with or without the ring 28 can now bethreaded into the opening so far provided. Body member I0 may bethreaded into position using any of the wrench-receiving surfaces 18, or26. The opening 44 in the member to be fitted with a pin is thensimilarly bored and counterbored, as shown in FIG. 9.

It is a further feature of the invention, that guide pins be made in twopieces comprising a machinable body portion 10, and a hardened pininsert 52 having external threads 30a that are identically shaped withthose of the bushings. Those portions of the pin insert 52 whichcorrespond in shape to those of the guide bushing rings are designatedby a like reference numeral characterized further in that a suffix a isaffixed thereto. A properly shaped pin for use in the present inventionis shown in FIGS. 10 and 11. The pin insert 52 has a projection 54having a cylindrically shaped guide surface 56 having a sliding fit withrespect to the opening 32 or surfaces 42, as the case may be. A taperedguide surface 58 projects from the cylindrical surface 56, and the endof the projection 54 is polygonal-shaped as at 60 to receive a wrench.The pin insert 52 preferably also has a pilot or guide portion 62 havingcylindrical sidewalls that have a sliding fit with respect to thesidewalls of the opening 22 of the body 10. The guide portion 62 has anaxially extending opening 64 in the bottom end thereof for receiving atool which will permit the pin 52 to be unthreaded from the body 10 whenthe projection 54 is broken or damaged. In the preferred embodiment, thesidewalls of the opening 64 are provided with four equally spacedgrooves 66 adapted to receive the comers of a square bar. Alternatively,the opening 64 may be given a hexagonal shape, or may be threaded sothat torque can be provided to the pin 52. The bushing 10 which receivesthe pin insert 52 need not be identically shaped with that for receivingthe ring 28, and numerous changes could be made thereto, as for exampleby interchanging the guide portion 62 and threaded portion 30a, or byproviding a seating shoulder for limiting threaded insertion of the pinin the body. The wrench-receiving opening 64 can also be used toadvantage in conventional one-piece guide pins that do not include theremovable body 10.

The opening 32 of the ring shown in FIGS. 1 and 2 has a diameter equalto the spacing of the surfaces 42. After the body portion 10 of thebushings of the present invention are threaded into the openings 44 tobring their flange portions 12 into firm tight engagement with thebottom of the counterbore 48, the hardened ring 28 is threaded into thethreads 24 of the body 10 until its top surface is flush or slightlybelow the top surface of the flange 12. In those instances where thering 28 contains a cylindrical opening 32, the installation is completedby simply locking it in position relative to the body member. This maybe accomplished by placing a staking tool through the opening 36 of thebushing when provided and deforming the portion of the threads 24 thatare exposed by the opening 36. In those instances when the ring or pininsert 52 is provided with the hemicylindrically shaped groove 38, adrill of the proper diameter is centered on the body 10 using thesurface 38 as a guide, and the body member 10 drilled to a suitabledepth. Thereafter, a soft metal pin, not shown, is placed in the openingthus provided to lock the ring 28 or pin against rotation.

In those instances where the bushing 10 is to be provided with a ringhaving an oblong opening 40 therein, the ring is threaded into thethreads 50 until its top surface is flush or slightly below the topsurface of the flange 12. A tool having a projection which tightlyengages the surfaces 42 is placed into the opening 40 and the toolrotated until the guide surfaces 42 exactly correspond with thedirection of thermal expansion. The tool is removed, and the ring islocked into position, either by staking the threads 24 through a recess35 or 36, or

by drilling the body 10 adjacent the groove 38 and placing a pintherein, as previously described.

In the most preferred embodiment, the guide pin inserts 52 have pinportions 54 thereon which are harder than are the guide rings, so thatsliding of the pins in the guide bushings produce wear of the ringportions rather than the pin portions 54. After the guide surfaces 32 or42, as the case may be, of the bushing have become worn, a wrench isplaced into the wrench-receiving surfaces of the ring and the ring isrotated relative to the body member 10. In the case of an oblong opening40, the wrench may have a shape corresponding to the shape of the oblongopening 40, and in the case of a cylindrical opening, a square bar maybe inserted into the grooves 34 or wrench openings machined into theupper surface of the ring 28 as previously described. Rotation of thehardened rings will machine out the staked section of the threads 24where this has been the means used to lock the ring in place. Where asoft pin has been used to engage the surface of the groove 38, thehardened ring will shear off the softened pin used to lock the ring inplace. After the ring is removed, a new ring having unwom surfaces canbe inserted and locked in place in the same manner previously described.If it is desired to remove the bushing body 10 after the ring isremoved, a wrench can be caused to engage one or more of thewrenchengaging surfaces 18, 20, 26, 42 or 60 and the relatively soft ormachinable body can be removed. If for any reason it is not possible tounthread the body member 10, it is possible to machine out the bodymember 10, since all of the hardened portions were removed with the ringor pin insert. It will rarely be necessary to remove the body member 10,however, even where the structures in which the body member 10 is frozenin an aluminum casting since all of the guiding surfaces are replaceableinserts. The body members and the inserts are preferably made of steel,and by using a never seize compound between the insert and body, theywill almost always separate.

It will now be seen that the objects heretofore enumerated as well asothers have been accomplished, and that there have been providedbushings and pins having standard dimensions which can be interchanged.It is further seen that the bushings of the present invention can havetheir guide surfaces accurately adjusted, and that these hardened guidesurfaces can be easily and quickly removed and be replaced withoutdamage to the main body portion of the bushing or to the member in whichthe bushing is installed. Replacement of the hardened guide surfaces canbe done from the front face of a shell-molding machine, or a hotboxforming machine, without cooling or disassembling the machine. It willfurther be seen that bushings of different press fit diameters need notbe provided, and that tools of standard diameter can be used for theformation of all openings in the equipment in which the pins andbushings are to be installed.

While the invention has been described in considerable detail, we do notwish to be limited to the particular embodiments shown and described,and it is our intention to cover hereby all novel adaptions,modifications and arrangements thereof which come within the practice ofthose skilled in the art to which the invention relates.

We claim:

1. A guide pin and guide assembly for accurately aligning core boxes andthe like, said assembly comprising: a pair of annular bodies each havingan axially extending external cylindrical centering surface, said bodiesbeing machinable and having threaded axially extending internalopenings, one of said bodies having an axially extending threaded pininsert threaded into its internal opening and projecting therefrom toform the guide pin of the assembly, said pin insert having an externalcylindrical guide surface of a predetermined diameter, the other one ofsaid bodies having an axially extending threaded ring insert threadedinto its internal opening, said ring being hardened to a generallynonmachinable condition and the inside of said annular ring having guidesurfaces for engaging and guiding said cylindrical guide surface of saidpin,

3. The pin-and-bushing assembly of claim 1 wherein the guide surfaces ofsaid guide pin are harder than said guide surfaces of said guidebushing.

1. A guide pin and guide assembly for accurately aligning core boxes andthe like, said assembly comprising: a pair of annular bodies each havingan axially extending external cylindrical centering surface, said bodiesbeing machinable and having threaded axially extending internalopenings, one of said bodies having an axially extending threaded pininsert threaded into its internal opening and projecting therefrom toform the guide pin of the assembly, said pin insert having an externalcylindrical guide surface of a predetermined diameter, the other one ofsaid bodies having an axially extending threaded ring insert threadedinto its internal opening, said ring being hardened to a generallynonmachinable condition and the inside of said annular ring having guidesurfaces for engaging and guiding said cylindrical guide surface of saidpin, and means for nonrotatably locking said ring in said other one ofsaid bodies.
 2. The pin-and-bushing assembly of claim 1 wherein thebodies of said pin and bushing are interchangeable.
 3. Thepin-and-bushing assembly of claim 1 wherein the guide surfaces of saidguide pin are harder than said guide surfaces of said guide bushing.